The internal anal sphincter in anorectal malformation

Area of Science:

• Pediatric Surgery
• Gastroenterology
• Anorectal Physiology

Background:

• A smooth muscle layer resembling the internal anal sphincter is present in high and intermediate anorectal malformations.
• The role of this rectal smooth muscle in anal continence requires further investigation.

Purpose of the Study:

• To investigate the influence of rectal mobilization on anal function and the internal anal sphincter's role in continence.
• To evaluate the function of the rectal smooth muscle thickening and rectal end-preserving operations in anorectal malformations.

Main Methods:

• Chronic animal experiment in dogs (n=15) involving rectal separation, internal anal sphincter resection, or both, with 24-week anorectal manometry.
• Clinical study in infants (n=5) with high/intermediate anorectal malformations, including preoperative and postoperative manometry of the rectal end and clinical follow-up.

Main Results:

• In dogs, rectal separation caused transient mild anal dysfunction, while internal anal sphincter resection led to persistent severe dysfunction.
• Preoperative manometry in infants showed rhythmic activity and reflex pressure changes in the rectal end.
• Rectal end-preserving surgery maintained rectal end activity and rectoanal reflex in most infants, with good clinical outcomes anticipated.

Conclusions:

• The functional internal anal sphincter at the rectal end in anorectal malformations plays an essential role in anal continence.
• Utilizing the rectal end during reconstructive surgery is recommended due to its contribution to anal continence.